U.S. patent application number 12/266297 was filed with the patent office on 2009-05-07 for self-centering control rod.
This patent application is currently assigned to Fallbrook Technologies Inc.. Invention is credited to Curtis W. Malone.
Application Number | 20090114058 12/266297 |
Document ID | / |
Family ID | 40586810 |
Filed Date | 2009-05-07 |
United States Patent
Application |
20090114058 |
Kind Code |
A1 |
Malone; Curtis W. |
May 7, 2009 |
SELF-CENTERING CONTROL ROD
Abstract
Embodiments include a self-centering control rod device having
two independently operating springs, a bushing, and a control rod.
The two springs utilize preload compression to maintain the control
rod centered. One spring operates directly against the control rod
while the other operates against the bushing. Each spring may have
different spring strength or established preload in order to
balance out the application force required to control a particular
object. Spring compression force adjustments on one spring do not
affect the center point or the spring compression force adjustment
of the other spring.
Inventors: |
Malone; Curtis W.; (Mustang,
OK) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
Fallbrook Technologies Inc.
San Diego
CA
|
Family ID: |
40586810 |
Appl. No.: |
12/266297 |
Filed: |
November 6, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60986159 |
Nov 7, 2007 |
|
|
|
Current U.S.
Class: |
74/592 |
Current CPC
Class: |
G05G 23/02 20130101;
Y10T 74/2158 20150115; G05G 5/05 20130101 |
Class at
Publication: |
74/592 |
International
Class: |
G05G 1/00 20060101
G05G001/00 |
Claims
1. A self-centering control rod apparatus for maintaining a control
rod in an equilibrium position when no external operating forces
are applied, the apparatus comprising: at least one support
bracket; a bushing; a first spring, wherein the first spring has a
means for establishing a spring preload, and wherein the first
spring preload acts to maintain the position of the bushing
relative to the support bracket; and a second spring, wherein the
second spring has a means for establishing a spring preload, and
wherein the second spring preload acts to maintain the position of
the control rod relative to the bushing, and wherein the preload of
one spring does not directly counter the preload of the other
spring.
2. The device of claim 1, wherein the means for establishing the
first or second spring preload is adjustable.
3. The device of claim 1, wherein the means for establishing the
first or second spring preload is fixed.
4. A self-centering control rod apparatus for maintaining a control
rod in an equilibrium position when no external operating forces
are applied, the apparatus comprising: a first and second support
bracket, each with a collinear opening; a bushing supported by the
first and second support bracket openings such that the bushing
passes through both support bracket openings and linearly
translates relative to the support brackets, the bushing
comprising: an axial centrally located opening through which the
control rod linearly translates relative to the bushing; and a
first and second spring preload device, each preload device
positively retained by the bushing, wherein the first spring
preload device is located on one end of the bushing outside of the
space between the brackets while the second spring preload device
is located near the center of the bushing in the space between the
brackets; a first spring attached to the control rod by an
attaching means on the end outside of the first bracket, wherein
the spring end opposite the attaching means abuts the first spring
preload device, and wherein the spring is partially compressed
between the attaching means and the first spring preload device; a
second spring, wherein one end of the second spring abuts the first
bracket on the inside of the first bracket and the other end of the
second spring abuts the second preload device, and wherein the
second spring is partially compressed between the first bracket and
the second spring preload device; and a travel stop device retained
by the control rod such that the travel stop device maintains
contact with the bushing, at the bushing end opposite that of the
first spring preload device and outside the first support bracket,
when no external operator forces are applied.
5. The device of claim 4, wherein at least on of the first and
second spring preload devices is adjustable.
6. The device of claim 4, wherein at least on of the first and
second spring preload devices is fixed.
7. The device of claim 4, wherein the attaching means is
adjustable.
8. The device of claim 4, wherein the attaching means is fixed.
9. The device of claim 4, wherein the travel stop is
adjustable.
10. The device of claim 4, wherein the travel stop is fixed.
11. A self-centering control rod apparatus for maintaining a
control rod in an equilibrium position when no external operating
forces are applied, the apparatus comprising: a support bracket,
wherein the support bracket has a first and second support area,
each support area separated by a distance and having an opening
with both openings collinear; a bushing supported by the first and
second support area openings such that the bushing passes through
both openings and linearly translates relative to the support
bracket, the bushing comprising: an axial centrally located opening
through which the control rod linearly translates relative to the
bushing; and a first and second spring preload device, each preload
device positively retained by the bushing, wherein the first spring
preload device is located on one end of the bushing outside of the
space between the first and second support areas while the second
spring preload device is located near the center of the bushing in
the space between the first and second support areas; a first
spring attached to the control rod by an attaching means on the end
outside of the bracket, wherein the spring end opposite the
attaching means abuts the first spring preload device, and wherein
the spring is partially compressed between the attaching means and
the first spring preload device; a second spring, wherein one end
of the second spring abuts the bracket on the first support area in
the space between the first and second support areas and the other
end of the second spring abuts the second spring preload device,
and wherein the second spring is partially compressed between the
bracket and the second spring preload device; and a travel stop
device retained by the control rod such that the travel stop device
maintains contact with the bushing, at the bushing end opposite
that of the first spring preload device and outside the support
bracket, when no external operator forces are applied.
12. The device of claim 11, wherein at least one of the first and
second spring preload devices is adjustable.
13. The device of claim 11, wherein at least one of the first and
second spring preload devices is fixed.
14. The device of claim 11, wherein the attaching means is
adjustable.
15. The device of claim 11, wherein the attaching means is
fixed.
16. The device of claim 11, wherein the travel stop is
adjustable.
17. The device of claim 11, wherein the travel stop is fixed.
18. A method of maintaining a control rod in an equilibrium
position, the method comprising the steps of: operably coupling at
least one support bracket to a bushing; operably coupling a first
spring to the bushing; operably coupling a second spring to the
bushing; establishing a first spring preload on the first spring
relative to the support bracket; and establishing a second spring
preload on the second spring, wherein the first spring preload is
separate from the second spring preload.
19. The method of claim 18, wherein establishing a first spring
preload comprises providing at least one adjustable spring preload
member.
20. The method of claim 18, wherein establishing a first spring
preload comprises providing a fixed spring preload member.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 60/986,159, filed on Nov. 7, 2007, which is
hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a self-centering control
rod linkage that is free to move linearly yet automatically returns
to center when the actuating force is removed.
[0004] 2. Description of Related Art
[0005] Certain industrial processes require a control rod mechanism
that will move freely in a linear direction (i.e., "side-to-side"
or "back-and-forth") yet return to center when the operator removes
the actuating force. For example, a typical hydraulic sliding spool
valve may be connected to a self-centering linkage. The spool valve
may have a center position with ports configured such that movement
of the spool in one direction from center opens a certain
combination of ports. Likewise, movement of the spool in the
opposite direction from center opens a different combination of
ports. At rest the spool is intended to remain in a neutral center
position.
[0006] Such a spool valve may feature a handle attached to the end
of a control rod linkage that is attached to an end of the spool.
Prior art self-centering control rod linkages (such as that
depicted in FIG. 1) typically utilize a control rod that passes
through an opening in some type of support bracket. Springs on
either side of the bracket are then attached to the control rod by
either a fixed or adjustable collar. The collar traps the spring
between the face of the collar and the bracket. With a spring and
collar on both sides of the center bracket, the spring preload
force positions the rod such that the compressed spring forces on
either side of the bracket are balanced and the rod is in a neutral
position (equilibrium).
[0007] A self-centering control rod linkage is also used in some
applications involving certain vehicle transmissions. For example,
a continuously variable transmission such as that disclosed in U.S.
Pat. No. 6,419,608 (titled "Continuously Variable Transmission" and
owned by Fallbrook Technologies) uses a self-centering control rod
to shift the transmission between its ranges
(forward-neutral-reverse). With the control rod in the center
position, the transmission is in neutral. If the control rod is
moved one direction from center, power is transferred through the
transmission such that it propels the vehicle forward. Movement of
the control rod in the opposite direction from center places the
transmission in reverse. Accordingly, a need exists for improved
self-centering control-rods.
SUMMARY
[0008] The system, method, and devices of the invention each have
several aspects, no single one of which is solely responsible for
its desirable attributes. Without limiting the scope of this
invention as expressed by the claims which follow, its more
prominent features will now be discussed briefly. After considering
this discussion, and particularly after reading the section
entitled "Detailed Description of Certain Embodiments" one will
understand how the features of this invention can provide
advantages including those described herein.
[0009] One embodiment utilizes a control rod that is partially
encircled by a bushing. The bushing is supported by two independent
support brackets (one to the left and one to the right). Both the
bushing and the control rod are free to move linearly, relative to
one another, and both relative to the brackets. Two independent
springs, one on either side of one of the brackets, provide the
force necessary to retain the control rod in the center position.
One end of the control rod is typically attached to a device to be
controlled while the other end is attached to an actuator, such as
a handgrip or lever. The springs are retained such that an operator
applying force to the actuator will cause the control rod to move
relative to the brackets. As the control rod is moved to the left
(axially), the rightmost spring is compressed and the leftmost
spring is unaffected. Conversely, as the control rod is moved to
the right the leftmost spring is compressed and the rightmost
spring is unaffected. Because only one spring is ever affected upon
moving the control rod in a given direction, each spring can
utilize different spring pressures. This allows the embodiment to
be tuned such that the operator feels a balanced force at the
actuator even if the device under control has differing
activation/deactivation force requirements.
[0010] The springs can be adjusted independently without upsetting
the center point balance. The rightmost spring contacts the control
rod at one end and contacts a preload device on the rightmost end
of the bushing, and thus acts to apply force between the control
rod and the bushing. The leftmost spring contacts one support
bracket and maintains pressure on another preload device attached
to the bushing. The spring pressure from the rightmost spring
forces the bushing interference device against a stop on the
leftmost support bracket. Thus, with no external force applied to
the control rod, the system is in this equilibrium state.
Adjustments to the center position can be made by moving the stop
attached to the leftmost support bracket.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The present invention will be more fully understood by
reference to the following detailed description of the preferred
embodiments of the present invention when read in conjunction with
the accompanying drawings, wherein:
[0012] FIG. 1 depicts a prior art self-centering control rod;
[0013] FIG. 2 depicts a frontal view of a preferred embodiment of
the present invention;
[0014] FIG. 3 depicts an isometric view of the same embodiment;
and
[0015] FIG. 4 depicts a cutaway isometric view of the embodiment to
improve the differentiation between the various component
parts.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS
[0016] The above figures are provided for the purpose of
illustration and description only, and are not intended to define
the limits of the disclosed invention. Use of the same reference
number in multiple figures is intended to designate the same or
similar parts. Furthermore, when the terms "top," "bottom,"
"right," "left," "rightward," "leftward," "first," "second,"
"upper," "lower" "height" "width" "length" "end" "side"
"horizontal" "vertical" and similar terms are used herein, it
should be understood that these terms have reference only to the
structure shown in the drawing and are utilized only to facilitate
describing the particular embodiment. The extension of the figures
with respect to number, position, relationship, and dimensions of
the parts to form the preferred embodiment will be explained or
will be within the skill of the art after the following teachings
of the present invention have been read and understood.
[0017] Current self-centering control rod devices face numerous
problems. One problem is that the balance of forces on both sides
of the return mechanism is highly temperamental. This creates a
system that is difficult to establish and maintain balanced in an
equilibrium state. If the application requires any precision as to
the exact center point, virtually no drift is allowed. However,
aging and other environmental factors (such as heat) cause spring
tensions to change and the center point to shift. Current
self-centering devices must be continually calibrated to compensate
for these changes or the device may continually drift.
[0018] Another problem with current self-centering control rod
devices is the force balance required to operate the device. Such a
device must have equilibrium of force between the opposing
centering springs to remain centered. However, the valve or
transmission to which the self-centering device is attached may
require a greater force to move in one direction as opposed to the
other. For example, a spool valve may be moving against a greater
fluid pressure when moved to the right yet have very little
pressure when moving the spool to the left. With current
self-centering devices, this differing application force will be
felt by the operator.
[0019] Yet another problem with current self-centering control rod
devices is the oscillations that can occur about the center point.
Current self-centering mechanisms featuring opposing compressed
springs that maintain opposing pressure on the centering bracket.
However, springs are notorious for oscillations. These spring
oscillations pass from side to side resulting in a mechanism whose
center point drifts from side to side at the frequency of
oscillation.
[0020] Accordingly, a need exists for a self-centering control rod
mechanism that is simple to calibrate, maintains calibration under
environmental and operational extremes, and minimizes oscillations
about the center point. Further, a need exists for a self-centering
control rod mechanism that balances the application force felt by
the operator regardless of differing forces required by the device
under control. Embodiments disclosed herein address these needs and
others as shown herein
[0021] FIG. 2 depicts a preferred embodiment of the present
invention. This embodiment features a control rod (102) encircled
by a bushing (126). The control rod (102) and bushing (126) are
free to move linearly relative to one another. The bushing (126)
passes through openings in a leftmost support bracket (104) and a
rightmost support bracket (116). The bushing (126) is also free to
move linearly relative to the support brackets (104 and 116).
[0022] In this embodiment, the leftmost support bracket (104)
features a support area (106) with a leftward travel stop (108).
This travel stop (108) serves to maintain the position of the
bushing (126) when at rest (equilibrium). A leftmost coil spring
(112) encircles the bushing (126) and abuts the left side of the
rightmost support bracket (116). A support area (114) on this
bracket serves to maintain position on the spring (112) to keep it
from contacting the bushing (126). Threads near the center of the
bushing (126) allow for positioning of locknuts (110) to establish
desired leftmost spring (112) preload pressure. The amount of
preload on this spring (112) determines the amount of return force
applied to the control rod (102) via the bushing (126) when the
control rod (102) returns to the left upon removal of externally
applied actuating forces.
[0023] The present embodiment also features a rightmost spring
(122) that encircles the control rod (102) to the right of the
rightmost support bracket (116). In this embodiment, the end of the
spring (122) farthest from the bracket (116) is held in place on
the control rod (102) by an adjustable collar (124). This
adjustable collar (124) serves as an attaching means for attaching
the spring (122) to the control rod (102).
[0024] The side of the spring opposite the attaching means abuts a
locknut (120) placed on the rightmost end of the bushing (126). As
before, this locknut (120) serves to establish the amount of
preload on the rightmost spring (122). The amount of preload on
this spring (122) determines the amount of return force applied to
the control rod when the control rod (102) returns to the right
upon removal of externally applied actuating forces. A second
adjustable collar serves as a rightward travel stop (118) to limit
the rightward motion of the control rod (102) at rest
(equilibrium).
[0025] FIG. 3 and FIG. 4 depict an isometric view of the claimed
apparatus to allow improved differentiation between the various
component parts. The cutaway view in FIG. 4 shows how the control
rod (102) passes entirely through the central portion of the
bushing (126). Further, the view shows the extent to which the
bushing (126) passes through the support brackets (104 and
116).
[0026] As stated previously, the present embodiment provides
distinct, positive stops for each direction of travel (leftward and
rightward travel stops, 108 and 118, respectively). Consequently,
the apparatus is not susceptible to oscillations about the
equilibrium point as are the prior art self-centering devices. The
prior art self-centering devices utilize balanced spring pressures
on either side of a center bracket to maintain equilibrium. Thus,
the natural harmonic oscillations generated in a spring are
transferred from one side to the other. In the present invention,
the positive stops (118 and 108) drastically reduce or prevent such
transfer.
[0027] In another embodiment, the two brackets (104 and 116) are
combined into a single bracket. This single bracket, however,
features two distinct support areas (such as 106 and 114 in FIG.
2). Thus, a single bracket may be fashioned to provide support for
the claimed apparatus. Sufficient distance is required between the
support areas to allow for movement of the leftmost spring preload
device (110).
Leftward Displacement of the Control Rod
[0028] When the control rod (102) is forced to the left, the
leftward travel stop (108) contacts the stationary support area
(106). This prevents the bushing (126) from moving to the left.
This also has the effect of maintaining the rightmost preload
device (120) stationary. The preload from the rightmost spring
(122) bears against the rightmost preload device (120) which keeps
the leftward travel stop (108) seated against the support area
(106), because the relative spacing between the rightmost preload
device (120) and the leftward travel stop (108) is fixed during
device setup. Thus, when the control rod (102) is forced to the
left, the adjustable collar (124) will compress the rightmost
spring (122) in proportion to the leftward displacement of the
control rod (102). Because the rightmost bracket (116) remains
stationary as does the leftmost preload device (110) during
leftward displacement of the control rod (102), the leftmost spring
(112) remains constant and unaffected in its preload state. When
the external actuating force is removed from the control rod (102),
the increased spring pressure in the rightmost spring (122) forces
the control rod (102) back until the rightward travel stop (118)
contacts the bushing (126). The apparatus is then in its
equilibrium state (center point).
Rightward Displacement of the Control Rod
[0029] When the control rod (102) is forced to the right, the
bushing (126) is consequently forced to the right due to contact
with the rightward travel stop (118). Because the rightmost support
bracket (116) is stationary, rightward movement of the bushing
(126) results in compression of the leftmost spring (112) in
proportion to the rightward displacement of the control rod (102).
Because the rightmost preload device (120) moves with the bushing
(126), the rightmost spring (122) remains constant and unaffected
in its preload state. When the external actuating force is removed
from the control rod (102), the increased spring pressure in the
leftmost spring (112) forces the bushing (126) back to the left
until the leftward travel stop (108) contacts the stationary
support area (106). Since the bushing (126) is always in contact
with the rightward travel stop (118) which is in turn fixed to the
control rod (102), the control rod (102) is forced to move leftward
in synchronous travel with the bushing (126).
Construction of the Apparatus
[0030] The present embodiment allows for use of materials suitable
for any particular application. For example, the control rod (102)
must be manufactured from a material or materials with qualities
that can withstand the types of forces that it will encounter. In
the present embodiment, the control rod (102) is made of metal. The
use of metal affords durability, strength, rigidity, and
machineability over softer materials, and allows the control rod
(102) to withstand compressive and tensile stresses experienced in
operation. However, other materials, such as plastic or plastic
composites may be used so long as the rod is capable of
withstanding the environmental extremes in which it operates. Any
suitable material may be utilized without exceeding the scope of
the present invention.
[0031] The shape of the control rod (126) in the present embodiment
is cylindrical. However, other cross-sectional shapes (such as a
triangular, square, rectangular, or oval) may be utilized depending
on the application requirements. For example, a particular
cross-section shape may provide additional rigidity in a particular
application and may be preferable over a standard circular cross
section. Any suitable shape may be utilized without exceeding the
scope of the present invention.
[0032] Likewise, the bushing (126) is made of metal to withstand,
primarily, the compressive stresses it encounters in operation. The
material chosen should be sufficiently durable, rigid, and
machineable to prevent undue deflection or distortion of the
bushing (126). This is important because the control rod (102) must
be free to move within the bushing (126), relative to the bushing
(126). In addition, the bushing (126) must be free to move within
the brackets (104 and 116), relative to the brackets (104 and 116).
Any such suitable material may be utilized without exceeding the
scope of the present invention.
[0033] The shape of the bushing (126) in the present embodiment is
cylindrical. However, other cross-sectional shapes (i.e.,
triangular, square, rectangular, oval, etc.) maybe utilized
depending on the application requirements. For example, a
particular cross-section shape may provide additional rigidity in a
particular application and may be preferable over a standard
circular cross section. Any suitable shape may be utilized without
exceeding the scope of the present invention. If a different shape
is utilized, the openings in the brackets (104 and 116) through
which the bushing (126) must pass must correspond. Likewise, the
central opening in the bushing (126) through which the control rod
(102) must pass must also correspond with the control rod (102)
cross-sectional shape.
[0034] The brackets (104 and 116) in the present embodiment are
metal and are designed to provide adequate support to the overall
device. The brackets (104 and 116) are also sufficiently rigid to
allow the springs to operate without undue deflection. The shape
and materials of the brackets (104 and 116) are immaterial and any
shape or material chosen is within the scope of the present
invention.
[0035] To improve the operation of the present invention, certain
coatings or lubricants may be utilized on the material surfaces.
For example, the bushing (126) may utilize soft-metal or polymer
coatings on its inner and/or exterior friction surfaces. Further,
such friction reducing materials may be utilized on the control rod
(102) and/or bracket (104 and 116) friction surfaces as well. Use
of friction reducing materials is within the scope of the present
invention.
[0036] The present embodiment features the use of an adjustable
collar (124) as an attaching means for attaching the spring (122)
to the control rod (102). It will be appreciated that other
attaching means, such as clamps, threaded nut, welded washers, a
machined feature, or the like, may be employed without departing
from the scope of the present invention. For example, another
embodiment of the present invention may feature a washer-type shape
welded to the control rod, against which the spring force is
applied. The present invention merely dictates that an attaching
means be supplied that is sufficient to maintain contact between
the spring and the rod. The scope of the present invention is
intended to encompass all equivalent structures.
[0037] While the present embodiment utilizes an adjustable collar
for the rightward travel stop (118), other means, such as a clamp,
threaded nut, welded washer, machined feature, or the like, may be
used without departing from the scope of the present invention. The
means chosen for the travel stop (118) must be suitable to maintain
contact between the control rod (102) and the bushing (126),
without slippage of the stop (118) due to impact by the bushing
(126). The scope of the present invention is intended to encompass
all equivalent structures.
[0038] This embodiment uses a nut for a leftward travel stop (108).
However, other means, such as a clamp, welded washer, machined
feature, or the like, may be utilized for the stop (108) and are
within the scope of the present invention. For example, the support
area (106) on the leftmost bracket (104) may have a machined flange
that serves as the leftward travel stop.
[0039] Two different locknuts (110 and 120) are featured in the
present embodiment. These locknuts (110 and 120) are attached to
the bushing (126) in two distinct locations. These adjustable
locknuts serve as spring preload devices. While the present
embodiment utilizes adjustable nuts (110 and 120) for the preload
devices, other means may be utilized and are within the scope of
the present invention. For example, the rightmost end of the
bushing (126) may feature a raised machined flange against which
the rightmost spring (122) may abut. Likewise, the leftmost nut
(110) could be replaced with a similar welded or machined flange
against which the rightmost spring (112) abuts and against which
the leftward travel stop (108) would impact.
[0040] One important aspect of the invention is the precision which
can be obtained in centering the control rod (102). This is
primarily due to the fact that the left and right springs (112 and
122) may be independently adjusted to establish preload. The
positive stops (118 and 108) dictate the control rod (102) center
point independent of the spring preload. Left spring (112) preload
ensures the leftward travel stop (108) remains seated against the
stationary support area (106). Right spring (122) preload ensures
the rightward travel stop (118) remains seated against the bushing
(126), which is stationary because the leftward travel stop (108)
is seated against the stationary support area (106). A change in
preload on either the right or left springs will only serve to vary
the external force required to actuate the control rod (102) in the
rightward or leftward direction.
[0041] To adjust the control rod (102) center point, loosen the
right spring attaching means (124) to remove the right spring (122)
preload pressure. If the attaching means (124) is not adjustable,
the rightmost preload device (120) can be adjusted instead. Next,
loosen the rightward travel stop (118). While maintaining the
leftmost travel stop (108) seated against the stationary support
area (106) and the rightmost travel stop (118) seated against the
bushing (126), position the control rod (102) as necessary. Next,
tighten the rightward travel stop (118) while maintaining contact
with the bushing (126). Restore right spring (122) preload by
repositioning the attaching means (124) and reestablishing proper
preload by adjusting the rightmost preload device (120).
[0042] The invention may be embodied in other specific forms
without departing from the spirit or essential characteristics
thereof. The present embodiments are therefore to be considered in
all respects as illustrative and not restrictive, the scope of the
invention being indicated by the appended claims rather than by the
foregoing description, and all changes which come within the
meaning and range of equivalency of the claims are therefore
intended to be embraced therein. Further, the recitation of method
steps does not denote a particular sequence for execution of the
steps. Such method steps may therefore be performed in a sequence
other than that recited unless the particular claim expressly
states otherwise.
* * * * *